SawJunkie
ArboristSite Member
Supposed to rain here tomorrow and figured it will be a good day to do a muff mod on my 390. It's the first saw I bought and has been good to me. I put a new 20" ES bar on it this afternoon as I have wore the original E bar out. My question is how much should I open up the muffler? Do I just pull the front plate off and drill one big hole or a series of smaller ones? How many RPM's can I safely turn after doing the mod? I was thinking around 13,500 but maybe thats too lean? I do have a tach. Info/advice/tips will be greatly appreciated!